JPH08277255A - Continuous production of urethane - Google Patents

Abstract

PURPOSE: To continuously obtain a urethane by controlling ammonia concentration and reaction temperature to raise reaction selectivity. CONSTITUTION: In a method for continuously producing a urethane by supplying a mixed solution containing a primary polyamine, urea and/or an N- nonsubstituted carbamic ester and an organic hydroxyl compound to a reaction column and extracting a reaction solution containing a formed urethane from the bottom of the reaction column while continuously pulling out evolved ammonia, (a) the temperature at the top of the reaction column is maintained at 100-180 deg.C and the temperature at the bottom of the reaction column is kept at 160-280 deg.C and made >=20 deg.C higher than that at the top of the reaction column and (b) the ammonia concentration in the reaction solution at the top of the reaction column is maintained at 0.01-10wt.% and that in the reaction solution at the bottom of the reaction column is kept at 0.1-300ppm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing urethane, which is widely used as a masked isocyanate and an intermediate raw material for isocyanate. More specifically, 1
-Grade polyamines with organic hydroxyl compounds and urea and /
Or by reacting with an N-unsubstituted carbamic acid ester,
The present invention relates to a continuous urethane production method in which by-produced ammonia is continuously reacted while being removed from a reaction system.

[0002]

2. Description of the Related Art Conventionally, isocyanates have been produced by reacting primary amines with phosgene. This method uses toxic phosgene, produces a large amount of corrosive hydrogen chloride gas as a by-product, Furthermore, it has the disadvantage that isocyanate and hydrolyzable chlorine compounds that are difficult to separate are by-produced, and this is mixed in the product.Therefore, the establishment of an industrial production method for isocyanates that does not use phosgene is strongly established. I have been asked.

Japanese Unexamined Patent Publication No. 55-120551 (US Pat. No. 4,297,501) discloses a method for producing an aliphatic O-aryl urethane without using phosgene.
A process for the oxidative urethanization of a primary amine, carbon monoxide and an aliphatic alcohol or an aromatic hydroxyl compound with a noble metal catalyst is described. However, this method also uses carbon monoxide, which is highly toxic, and uses an expensive noble metal catalyst. Therefore, it requires a complicated operation and a large cost to recover the catalyst from the urethane product. Have problems such as.

In US Pat. No. 3,873,553, N-alkyl-N ', N'-dialkylurea,
A method for producing an N-alkyl-O-aryl urethane by reacting an aromatic hydroxyl compound and hydrogen chloride gas is described. However, this method also uses corrosive hydrogen chloride gas and produces N,
The recovery of urethane from the hydrochloride of N'-dialkylamine has a problem that it requires a complicated operation and a large cost.

On the other hand, US Pat. No. 2,677,698 discloses a method for producing an aliphatic monourethane that does not use phosgene, wherein an aliphatic primary amine and urea are used to produce N, N'-dialkyl. Urea is made and N, N 'in the second stage
A method of reacting a dialkylurea with a hydroxyl compound to produce an aliphatic monourethane, separating and recovering a by-produced primary amine and returning it to the first stage. But,
Not only is this method low in urethane yield, but the reaction
Since it requires a step and a primary amine recycling facility, the process is extremely complicated and is not satisfactory for industrial implementation.

Further, JP-A-6-41045 discloses a method for producing an aliphatic O-alkyl polyurethane after producing a bisurea from an aliphatic primary polyamine, urea and an alcohol. However, this method is problematic in that the reaction has two stages and the residence time is very long. Further, some methods have been proposed for producing an aliphatic urethane by reacting an aliphatic primary amine with a hydroxyl compound and urea in a single step.

For example, US Pat. No. 2,409,712 describes a method of reacting an aliphatic primary amine and urea with an aliphatic alcohol to produce an aliphatic O-alkyl monourethane. . In addition, JP-A-55-1
Japanese Patent No. 45657 (West German Patent 2,917,493) describes a method for producing an aliphatic O-alkyl polyurethane by reacting an aliphatic primary polyamine with an aliphatic alcohol in the presence of urea or a urea compound. Has been done. Further, as an improved method of these, JP-A-56-103153
Japanese Patent (West German Patent 2,943,551) and Japanese Patent Laid-Open No. 56-56
-103153 (West German Patent No. 2,943,550) discloses a method for producing an aliphatic O-alkyl polyurethane by reacting an aliphatic primary polyamine with an aliphatic alcohol in the presence of urea and an N-unsubstituted urethane. Is listed.

The aliphatic urethanes obtained by the above-mentioned one-step method are all aliphatic O-alkyl urethanes. As described above, it is presumed that the O-aryl urethane is excluded because of the following description in the known literature. For example, by SR Sandler and W. Karo, "By Functional Group"
Organic Compound Synthesis Method II ”, p. 248 (published by Hirokawa Shoten in 1971), O-alkyl N-unsubstituted carbamates can be easily synthesized from urea and alcohol, but N-unsubstituted from urea and aromatic hydroxyl compounds. Carbamic acid O-
It is described that it is difficult to produce an aryl.

As a method for producing an aliphatic O-aryl urethane, JP-A-2-759 and JP-A-3-202 are known.
Japanese Patent Publication No. 54-54 discloses a method for producing an aliphatic O-aryl urethane from a one-step reaction of urea and / or O-aryl N-unsubstituted carbamate, an aromatic hydroxyl compound and an aliphatic primary amine. There is. These methods show considerable improvements in the removal of ammonia, such as the reactive distillation method and the introduction of an inert gas. However, in any case, only mentioning that the concentration of ammonia in the reaction solution is lowered, further, regarding the application to an alicyclic amine having a slow reaction rate among aliphatic amines,
Although methods such as increasing the reaction temperature to accelerate the reaction have been adopted, the yield is still unsatisfactory and improvements are needed.

[0010]

The problem to be solved by the present invention is to eliminate the above-mentioned drawbacks, that is, to provide a process for producing urethane in a high yield by increasing the reaction selectivity. Another object of the present invention is to provide a production method for improving the yield of urethane from an alicyclic amine having a particularly slow reaction rate.

[0011]

The present inventors have arrived at the present invention as a result of intensive studies to overcome the above-mentioned problems of the prior art. That is, the present invention relates to primary polyamines, urea and / or
Alternatively, an N-unsubstituted carbamic acid ester and an organic hydroxyl compound are continuously supplied to the reaction tower to generate a corresponding urethane, and ammonia generated in the reaction tower is continuously withdrawn from the reaction tower, and the generated urethane is In a continuous method for producing urethane, which comprises continuously withdrawing a mixed solution containing the same from the bottom of the reaction tower, a) the temperature of the upper part of the reaction tower is 100 to 180 ° C and the temperature of the lower part of the reaction tower is 1
The temperature of the lower part of the reaction tower is higher than the temperature of the upper part of the reaction tower by 20 ° C or more, and b) the ammonia concentration in the upper part of the reaction tower is 0.01-1.
0 wt%, the ammonia concentration in the mixed liquid at the bottom of the reaction column was maintained at 0.1 to 300 ppm, and the ammonia concentration in the liquid above the reaction column was higher than the ammonia concentration in the liquid below the reaction column. It is a continuous production method of urethane characterized by high price.

The present invention will be described in detail below. The organic hydroxyl compound used in the present invention includes aliphatic and aromatic hydroxyl compounds. The aliphatic hydroxyl compound may be any compound as long as the hydroxyl group is directly bonded to the aliphatic residue.
For example, aliphatic primary alcohols such as methanol, propanol, butanol, isobutanol, pentanol, isopentanol, hexanol and 2-ethylhexanol are preferable. Such aliphatic hydroxyl compounds may be used alone or in combination of two or more.

On the other hand, the aromatic hydroxyl compound may be any one as long as the hydroxyl group is directly bonded to the aromatic residue. For example,
Phenol; various alkylphenols such as cresol (each isomer), xylenol (each isomer), ethylphenol (each isomer), propylphenol (each isomer), methoxyphenol (each isomer), ethoxyphenol (each isomer) Alkoxyphenols such as chlorophenol (each isomer), bromophenol (each isomer), dichlorophenol (each isomer), dibromophenol (each isomer), and other halogenated phenols; methylchloro Alkyl- and halogen-substituted phenols such as phenol (each isomer), ethylchlorophenol (each isomer), methylbromophenol (each isomer), ethylbromophenol (each isomer); nitrophenol (each isomer), Nitro-substituted aromatic hydro such as nitronaphthol (each isomer) Sill compounds; cyanophenol (including isomers), cyano naphthol (isomers) cyano-substituted aromatic hydroxyl compounds such as and the like are used.

One such aromatic hydroxyl compound is
Only one kind may be used, or two or more kinds may be mixed and used. Further, it is preferable to use an aromatic monohydroxyl compound because it can be easily separated by distillation, and among them, phenol having a low boiling point is preferably used. Such aliphatic hydroxyl compounds may be used alone or in combination of two or more.

Examples of the primary polyamine used in the present invention include aliphatic primary polyamines and aromatic primary polyamines. An aliphatic compound having two or more primary amino groups bonded to an aliphatic carbon atom. It is preferably a primary polyamine, and may be an alicyclic primary polyamine or an araliphatic primary polyamine. Examples of such aliphatic primary polyamines include ethylenediamine, diaminopropane (each isomer), diaminobutane (each isomer), diaminopentane (each isomer), diaminohexane (each isomer), diaminodecane ( Aliphatic primary diamines such as isomers; triaminohexane (each isomer), triaminononane (each isomer), triaminododecane (each isomer), 1,8-diamino-4-aminomethyl -Octane, 2,6-diaminocapric acid-2-aminoethyl ester, 1,3,6-triaminohexane, 1,6,1
Aliphatic primary triamines such as 1-triaminoundecane, diaminocyclobutane, diaminocyclohexane (each isomer), 3-aminomethyl-3,5,5-trimethylcyclohexylamine, triaminocyclohexane (each isomer), di Acyclic aliphatic, alicyclic and araliphatic primary polyamines such as (aminomethyl) pyridine (each isomer) and di (aminomethyl) naphthalene (each isomer).

Further, in the aliphatic group, alicyclic group and aromatic group forming the skeleton of these primary polyamines, a part of hydrogen is halogen, alkyl group, alkoxy group, aryl group, ester group, It may be substituted with a substituent such as a sulfone group or a cyano group, and the skeleton is an unsaturated bond, an ether bond, an ester bond, a thioether bond,
It may contain a sulfone bond, a ketone bond, or the like.

The N-unsubstituted carbamic acid ester used in the present invention may be any one as long as an aminocarboxyl group (-OCONH2) is bonded instead of the hydroxyl group (-OH) of the organic hydroxyl compound used. It may be. For example, N-unsubstituted carbamate O-phenyl, N-unsubstituted carbamate O- (methyl)
Examples thereof include phenyl, N-unsubstituted carbamate O- (dimethyl) phenyl, N-unsubstituted carbamate O- (chloro) phenyl, and N-unsubstituted carbamate O-butyl.

The amount of the organic hydroxyl compound used in the practice of the present invention is preferably 2 mol or more and 200 mol or less per 1 equivalent of the amino group of the aliphatic primary polyamine used. If it is 2 times or less, the yield of urethane obtained will decrease. Further, if it is more than 200 mol, not only the space-time yield is lowered but also the recycled amount of the organic hydroxyl compound is increased.

The amount of urea and N-unsubstituted carbamic acid ester used in the present invention is such that the sum of urea and N-unsubstituted carbamic acid ester is 1 per 1 equivalent of the amino group of the aliphatic primary polyamine in the reaction system. It is preferably from 0.05 mol to 2 mol. When the sum of urea and N-unsubstituted carbamic acid ester is less than 1.05 mol per 1 equivalent of amino group of primary polyamine, N, N'-dialkylurea compound is by-produced, and when it is more than 2 mol, unreacted. This is because a large amount of N-unsubstituted carbamic acid ester remains and the recycled amount increases.

The ratio of urea to N-unsubstituted carbamic acid ester in the reaction system can take any value. N-unsubstituted carbamic acid ester is more expensive than urea, and when it is supplied as a raw material, urea is mainly used, and it is industrially preferable that the amount of N-unsubstituted carbamic acid ester is recycled. In carrying out the present invention, it is a preferable method to use an organic hydroxyl compound in an excess amount as a solvent, but an appropriate other solvent can also be used.
As the solvent, from the viewpoint of solubility, for example, aromatic hydrocarbons such as toluene, xylene, chlorobenzene, dichlorobenzene, and nitrobenzene; ether compounds such as dioxane, diethylene glycol dimethyl ether, and diethylene glycol diethyl ether; N, N dimethylformamide, Examples include amide compounds such as N, N dimethylacetamide.

The apparatus used in the practice of the present invention is of the reactive distillation column type, for example, packed columns or tray columns are preferred. The reaction mode is such that the raw material is fed to the uppermost stage of the reaction stage and the reaction is allowed to proceed while the raw material liquid is flowing down inside the reaction tower. In addition, the vapor generated at the bottom of the reaction tower is mostly refluxed by partial condensation at the top of the reaction tower, and the vapor that could not be condensed here is totally refluxed into the reaction tower by the condenser above. To do so. Then, a method of taking out by-product ammonia in a gaseous form from the crown and removing it is preferable. Here, the upper part of the reaction column means a part up to about 1/3 from the upper part of all reaction stages. Similarly, the lower part of the reaction tower means a part from the lower side of all reaction stages to about 1/3.

Surprisingly, in the above-mentioned reaction system, a method of flowing a refrigerant outside the reaction tower, or a method of putting a cooler inside, so that only the upper part of the reaction tower is heated to 100 to 180 ° C. Etc. to positively cool and vaporize the vapor generated at the bottom of the reaction tower to maintain the ammonia concentration in the upper part of the reaction tower at a high concentration of 0.01 to 10 wt%, and the lower part of the reaction tower to 20% higher than the upper part. It was found that the reaction selectivity of urethane formation was improved and the urethane yield was improved by about 2% or more when the by-product ammonia was positively removed by increasing the temperature by more than ° C.

Although this reaction is a very complicated reaction consisting of many elementary reactions, when the above reaction system is used,
In particular, the reaction occurring in the upper part of the reaction column seems to act favorably for the production of the target urethane. Therefore, in carrying out the present invention, the upper part of the reaction tower is 100 to 18
The temperature range is 0 ° C, while the lower part of the reaction tower is 160-2.
The reaction is carried out in the temperature range of 40 ° C. and at a temperature higher than the upper part of the reaction tower by 20 ° C. or more. More preferably, it is higher than the upper portion by 30 ° C. or more.

If the lower part of the reaction tower is reacted at a temperature lower than 160 ° C., not only the reaction rate is slow, but also the solubility of ammonia is high and the chemical equilibrium is disadvantageous, so that the yield of urethane is lowered. If the lower part of the reaction tower is reacted at a temperature higher than 240 ° C, urea or N-unsubstituted carbamic acid ester is significantly decomposed, the organic hydroxyl compound is dehydrogenated, or the product urethane is decomposed. Or denaturation may cause a decrease in yield.

According to the present inventors, there is a Fries rearrangement as a characteristic by-product in the case of O-aryl urethane, and this reaction rapidly increases at high temperature, and especially alicyclic O-aryl urethane. In that case it is remarkable. In this sense, the more preferable temperature range in the lower part of the reaction tower is 180 to 220 ° C. In carrying out the present invention, the amount of ammonia by-produced in the urethanization reaction system to be removed differs between the upper part and the lower part of the reaction column, as in the temperature conditions described above. In the upper part of the reaction tower, it is slightly different depending on the reaction temperature and the difference in basicity between the primary polyamine and the organic hydroxyl compound, but it is preferably 0.01 to 10 wt%, preferably 0.5 to 5 wt%. . On the other hand, in the lower part of the reaction tower, the ammonia concentration in the reaction solution is 30
It is very important that the ammonia concentration in the upper part is positively removed so that it becomes 0 ppm or less, and the ammonia concentration in the upper part is higher than that in the lower part. This is because when the ammonia concentration is 300 ppm or more, the urethane yield decreases due to the equilibrium shown in the formula (1). In order to further increase the yield of urethane, it is preferable to remove ammonia so that the concentration of ammonia in the reaction solution in the final stage of the reaction is 15 ppm or less.

R-NHCONH ₂ + Ar-OH / R-NHCOO-Ar + NH ₃ (1) R-NHCONH ₂ + R'-OH / R-NHCOO-R '+ NH ₃ (2) (in the reaction formula, "R-", "R'-" represents an aliphatic residue, and [Ar- "represents an aromatic residue.) As one of the preferred embodiments for removing ammonia by-produced in the reaction system, there is a reactive distillation method. That is, the reactive distillation method is a method of separating ammonia, which is sequentially generated during the reaction, in a gaseous state by distillation. In order to improve the distillation efficiency of ammonia, it can also be performed under boiling of a solvent or an organic hydroxyl compound.

Another embodiment is a method using an inert gas. This is a method in which ammonia produced as a by-product in the reaction system is separated from the reaction system by being entrained in an inert gas in a gaseous state. As such an inert gas, for example, nitrogen, helium, argon, carbon dioxide, methane, propane, etc. may be used alone or in a mixture, and then introduced into the reaction system. Also, a gaseous low-boiling point organic solvent can be used to remove the by-produced ammonia from the reaction system similarly to the inert gas. Examples of such low boiling point organic solvents include halogenated hydrocarbons such as dichloromethane, chloroform and carbon tetrachloride; lower hydrocarbons such as pentane, hexane, heptane, benzene, toluene and xylene; ketones such as acetone and methyl ethyl ketone. Ethers such as tetrahydrofuran and dioxane can also be used.

Further, in order to remove the ammonia by-produced in the reaction system, a reactive distillation method, a method using an inert gas or the like can be used in combination. In carrying out the present invention, the reaction pressure varies depending on the composition of the reaction system, the reaction temperature, the method for removing ammonia, the type of the reaction apparatus and the like, but it is usually preferable to carry out the reaction in the pressure range of 0.1 to 50 atm. . More preferably, a pressure range of 1 to 30 atm is preferable for industrial implementation.

Similarly, the reaction time varies depending on the composition of the reaction system, the reaction temperature, the method of removing ammonia, the type of the reaction apparatus, etc., but is usually several tens of minutes at the upper and lower parts of the reaction tower.
Dozens of hours. It is preferably several ten minutes to several hours. However, making urethane stay in the bottom of the reaction tower for a long time leads to decomposition of urethane and formation of Fries rearrangement, and in particular, Fries rearrangement rapidly increases at high temperature.
For this reason, it is necessary to withdraw so that the residence time at the bottom of the reaction tower is within 30 minutes.

Further, a catalyst may be used for the purpose of increasing the reaction rate. Examples of such catalysts include rare earth elements, antimony and bismuth simple substances and oxides, sulfides and salts of these elements; simple boron and boron compounds; copper group, zinc group, aluminum group and carbon of the periodic table. Group, titanium group metals and oxides and sulfides of these metals; carbon groups excluding carbon in the periodic table,
Carbides and nitrides of titanium group, vanadium group, and chromium group elements are preferably used. When a catalyst is used, the catalyst and the aliphatic primary amine can be used in any amount ratio, but the weight ratio to the aliphatic primary amine is usually 0.000.
It is preferable to use 1 to 100 times the amount of catalyst.

The process of the present invention is a masked isocyanate of 1,6-hexamethylene diisocyanate, which is suitable for producing O-aryl monourethanes and polyurethanes and which is used in industrially large amounts. , 6-
Preparation of hexamethylene-O, O'-diphenylurethane or dibutylurethane, 3-isocyanatomethyl-
3-phenoxycarbonylaminomethyl-a masked isocyanate of 3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate)
Production of 3,5,5-trimethyl-1-phenoxycarbonylaminomethylcyclohexane (isophorone diphenyl urethane) or dibutyl urethane, and m-xylylene-O, O-diphenyl urethane which is a masked isocyanate of m-xylylene diisocyanate It is also a method suitable for producing dibutyl urethane.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A system example and an execution flow of an apparatus for carrying out the method of the present invention for continuously producing urethane will be described below with reference to FIG. Further, the following examples and comparative examples were carried out based on the system example and the implementation flow. The corresponding substance streams are indicated by the numbers in parentheses.

In the mixing container A, the primary polyamine (1),
Urea (2) and / or N-unsubstituted carbamic acid ester (3) and organic hydroxyl compound (4) are mixed. The mixed solution (5) is fed to the uppermost plate of the reactive distillation column B by a pump. As the reactive distillation column B, an ordinary apparatus such as a packed column or a tray column is used, and here, a reactive distillation column having an inner diameter of 151 mm and a height of 12624 mm was used. The average residence time of the reactive distillation column B is 0.5 to 1.5 hours. About the upper one-third part of the reactive distillation column is forcibly cooled, for example, externally or internally, in order to reach a desired reaction temperature. Most of the vapor generated in the reboiler C at the bottom of the reaction column is condensed at the upper part of the reactive distillation column B, and the remaining vapor is condensed at the head by cooling water and refluxed into the reactive distillation column B, while in the system. The by-produced ammonia (6) is taken out as a gas from the top of the head. The reaction liquid (7) is obtained from the bottom of the reactive distillation column B. (Example 1) 1,6-hexamethylenediamine (HD
A) 4.408 kg, urea 5.244 kg, and N-
Phenol containing unsubstituted O-phenyl carbamate 14
A raw material liquid consisting of 2.88 kg was used. The reaction pressure is 1.
The conditions were 10 kg / cm ² -G, the upper temperature was 160 ° C., the lower temperature was 210 ° C., and the raw material supply rate was 7 kg / Hr. After completion of the reaction, the reaction solution is wholly recovered, and the weight% of 1,6-hexamethylene-O, O'-diphenylurethane (HDU) and ammonia (NH3) contained in the reaction solution.
Was quantified. From this value, the molar yield of HDU per the molar number of HDA charged was converted. Table 1 shows the results. (Examples 2 to 3) The same apparatus as in Example 1 was used, and the conditions were the same as in Example 1 except that the reaction pressure and temperature were changed. In Example 2, the reaction pressure was 1.10 kg / cm ² −.
G, the upper temperature was 120 ° C, and the lower temperature was 210 ° C. In Example 3, the reaction pressure was 2.00 kg / cm ² -G, the upper temperature was 160 ° C., and the lower temperature was 220 ° C.

Comparative Example 1 The same apparatus and the same raw material composition as in Example 1 were used, and the same conditions as in Example 1 were used except that the upper temperature was changed. In Comparative Example 1, the upper temperature was 200 ° C. Table 1 shows the results. (Examples 4 to 7) The same operation as in Example 1 was repeated except that the composition of raw materials,
The reaction was carried out under the same conditions as in Example 1 except that the reaction pressure, temperature, and average residence time in the reaction tower were changed as follows. A raw material liquid consisting of 6.460 kg of 3-aminomethyl-3,5,5-trimethylcyclohexylamine (IPDA), 5.244 kg of urea, and 160.74 kg of phenol containing N-unsubstituted O-phenyl carbamate was used. The reaction pressure is 0.85 kg / cm ² -G, the upper temperature is 160 ° C.,
The lower temperature was 205 ° C. The average residence time in the reaction tower is 3
It is 0 to 80 minutes. After completion of the reaction, the reaction solution was totally recovered and the weight% of 3-phenoxycarbonylaminomethyl-3,5,5-trimethyl-1-phenoxycarbonylaminocyclohexane (IPDU) and ammonia (NH3) contained in the reaction solution was determined. . From this value, the molar yield of IPDU per molar number of IPA charged was converted. In Example 4, the reaction pressure was 0.85 kg / cm ² -G, the upper temperature was 160 ° C., and the lower temperature was 205 ° C. In Example 5, the reaction pressure was 2.00 kg / cm ² -G and the upper temperature was 16
The temperature was 0 ° C and the lower temperature was 220 ° C. In Example 6, the reaction pressure was 3.95 kg / cm ² -G, the upper temperature was 160 ° C., and the lower temperature was 240 ° C. In Example 7, the reaction pressure was 0.85.
kg / cm ² -G, upper temperature 120 ° C., lower temperature 205
° C. The results are shown in Table 2. (Comparative Examples 2 to 4) The same apparatus as in Example 4 was used, and the same conditions as in Example 4 were used except that the reaction pressure and the temperature amount were changed. In Comparative Example 2, the reaction pressure was 0.85 kg / cm ² −.
G, the upper temperature was 190 ° C, and the lower temperature was 205 ° C. In Comparative Example 3, the reaction pressure was 2.00 kg / cm ² -G, the upper temperature was 210 ° C., and the lower temperature was 220 ° C. In Comparative Example 4,
Reaction pressure 3.95 kg / cm ² -G, upper temperature 230
The lower temperature was 240 ° C.

The results are shown in Table 2. (Examples 8 to 9) The same apparatus as in Example 4 was used, and the same conditions as in Example 4 were used except that the average residence time in the upper part was changed. In Example 8, the upper average residence time was 30 minutes.
In Example 9, the upper average residence time was 120 minutes. The results are shown in Table 2. (Example 10) The same apparatus as in Example 4 was used, and the same conditions as in Example 4 were used except that the raw material composition and the upper temperature were changed. In Example 10, 3-aminomethyl-3,5,5-
Trimethylcyclohexylamine (IPDA) 4.40
Phenol 112.48k containing 8 kg, urea 10.488 kg, and N-unsubstituted O-phenyl carbamate
A raw material liquid of g was used and the upper temperature was 140 ° C.
Table 3 shows the results. (Comparative Example 5) The same apparatus as in Example 4 was used, and the same conditions as in Example 4 were used except that the upper temperature was changed. In Comparative Example 5, the upper temperature was 200 ° C. Table 3 shows the results.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

[0039]

The present invention has the following advantages over the conventional method. 1) Actively cooling the upper part of the reaction tower to maintain the ammonia concentration in the liquid at 0.01 to 10 wt%, while maintaining the ammonia concentration in the liquid at 300 ppm or less in the lower part, and reacting By making the concentration of ammonia in the liquid at the top of the tower higher than the concentration of ammonia in the bottom of the reaction tower and by reacting while positively removing the by-product ammonia from the reaction system, it is possible to increase the reaction selectivity and increase the urethane content. It can be obtained in yield.

2) Since phosgene and carbon monoxide are not used, there are no problems of corrosion and toxicity, and a large amount of hydrogen chloride gas as a by-product. Furthermore, it is inexpensive because there is no need to use an expensive precious metal catalyst. 3) High urethane yield is advantageous in industrial implementation. Furthermore, when the urethane obtained is an O-aryl urethane, it is easy to thermally dissociate and is advantageous for use as a masked isocyanate, an intermediate raw material of an isocyanate, and the like.

[Brief description of drawings]

FIG. 1 is an explanatory diagram illustrating a system example and an implementation flow of an apparatus that implements the method of the present invention.

[Explanation of symbols]

 1, primary polyamine 2, urea 3, N-unsubstituted carbamic acid ester 4, organic hydroxyl compound 5, mixed solution 6, ammonia 7, reaction solution A, mixing vessel B, reactive distillation column C, reboiler

Claims (4)

[Claims] 1. A primary polyamine, urea and / or N
-Unsubstituted carbamic acid ester and organic hydroxyl compound are continuously supplied to the reaction column to generate a corresponding urethane, and ammonia generated in the reaction column is continuously extracted from the reaction column while containing the urethane formed. In a continuous method for producing urethane, which comprises continuously withdrawing the reaction liquid from the bottom of the reaction tower, a) maintain the temperature of the upper part of the reaction tower at 100 to 180 ° C and the temperature of the lower part of the reaction tower at 160 to 280 ° C And the temperature of the lower part of the reaction tower is higher than the temperature of the upper part of the reaction tower by 20 ° C. or more, and b) the concentration of ammonia in the liquid in the upper part of the reaction tower is 0.0
1 to 10 wt%, the ammonia concentration in the reaction liquid at the bottom of the reaction tower is maintained at 0.1 to 300 ppm, and the ammonia concentration in the liquid above the reaction tower is the ammonia concentration in the liquid below the reaction tower. Continuous production method of urethane characterized by higher than 2. The continuous production method for urethane according to claim 1, wherein the organic hydroxyl compound is an aromatic hydroxyl compound. 3. The N-unsubstituted carbamic acid ester is N-
The continuous production method of urethane according to claim 1 or 2, which is an unsubstituted O-aryl carbamate. 4. The continuous method for producing a urethane according to claim 1, wherein the primary polyamine is an aliphatic primary polyamine.